/*
 * Copyright 2010-2012 VMware and contributors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 */

package cn.wenhao.javaClassReload.jvm;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

/**
 * An invoker represents the result of a method lookup operation in the type hierarchy.
 * <p>
 * It encapsulates a reference to a resolved method implementation in a reloadable or non-reloadable type and provides
 * an 'invoke' method suitable for invoking that method implementation, and a 'createJavaMethod' to create a Java
 * {@link Method} instance that can be used to represent the method in the Java reflection API.
 * 
 */
public abstract class Invoker {

    private Method cachedMethod; // Cached for cases where we get call getJavaMethod multiple times.

    public abstract Object invoke(Object target, Object...params)
        throws IllegalArgumentException, IllegalAccessException, InvocationTargetException;

    public abstract int getModifiers();

    public abstract String getName();

    public abstract String getMethodDescriptor();

    public String toString() {
        return "Invoker(" + Modifier.toString(getModifiers()) + " " + getClassName() + "." + getName()
            + getMethodDescriptor() + ")";
    }

    public abstract String getClassName();

    protected abstract Method createJavaMethod();

    public String getParamsDescriptor() {
        String methodDescriptor = getMethodDescriptor();
        return methodDescriptor.substring(0, methodDescriptor.lastIndexOf(')') + 1);
    }

    public Class<?> getReturnType() {
        return getJavaMethod().getReturnType();
    }

    public final Method getJavaMethod() {
        if (cachedMethod == null) {
            cachedMethod = createJavaMethod();
        }
        return cachedMethod;
    }

}
